1. Department of Computer Engineering, Jeju National University, Jeju-si 63243, Republic of Korea
2. Big Data Research Center, Jeju National University, Jeju-si 63243, Republic of Korea
3. Department of Electronic Engineering, Jeju National University, Jeju-si 63243, Republic of Korea
4. School of Electronics, Electrical Engineering and Computer Science, Queen’s University Belfast, Belfast BT7 1NN, UK